Is there a /dev/null on Windows?

Question

What is the equivalent of /dev/null on Windows?

Answer 1

I think you want NUL, at least within a command prompt or batch files.

For example:

type c:\autoexec.bat > NUL

doesn't create a file.

(I believe the same is true if you try to create a file programmatically, but I haven't tried it.)

In PowerShell, you want $null:

echo 1 > $null

Answer 2

According to this message on the GCC mailing list, you can use the file "nul" instead of /dev/null:

#include <stdio.h>

int main ()
{
    FILE* outfile = fopen ("/dev/null", "w");
    if (outfile == NULL)
    {
        fputs ("could not open '/dev/null'", stderr);
    }
    outfile = fopen ("nul", "w");
    if (outfile == NULL)
    {
        fputs ("could not open 'nul'", stderr);
    }

    return 0;
}

(Credits to Danny for this code; copy-pasted from his message.)

You can also use this special "nul" file through redirection.

Answer 3

NUL in Windows seems to be actually a virtual path in any folder. Just like .., . in any filesystem.

Use any folder followed with NUL will work.

Example,

echo 1 > nul
echo 1 > c:\nul
echo 1 > c:\users\nul
echo 1 > c:\windows\nul

have the same effect as /dev/null on Linux.

This was tested on Windows 7, 64 bit.

Answer 4

Jon Skeet is correct. Here is the Nul Device Driver page in the Windows Embedded documentation (I have no idea why it's not somewhere else...).

Here is another:

• The null device in the registry
• Special file names
• More on file naming

Answer 5

NUL works programmatically as well. E.g. the following:

freopen("NUL", "w", stderr);

works as expected without creating a file. (MSVC++ 12.0)

Answer 6

If you need to perform in Microsoft Windows the equivalent of a symlink to /dev/null in Linux you would open and administrator's cmd and type:

For files:

mklink c:\path\to\file.ext NUL:

Or, for directories:

mklink /D c:\path\to\dir NUL:

This will keep the file/direcotry always at 0 byte, and still return success to every write attempt.

Answer 7

You have to use start and $NUL for this in Windows PowerShell:

Type in this command assuming mySum is the name of your application and 5 10 are command line arguments you are sending.

start .\mySum  5 10 > $NUL 2>&1

The start command will start a detached process, a similar effect to &. The /B option prevents start from opening a new terminal window if the program you are running is a console application. and NUL is Windows' equivalent of /dev/null. The 2>&1 at the end will redirect stderr to stdout, which will all go to NUL.